Plasma devices refer to devices configured for generating plasma. Such plasma can be used, for example, in surgery for destruction (dissection, vaporization) and/or coagulation of biological tissues.
As a general rule, such plasma devices have a long and narrow end that can be easily held and pointed toward a desired area to be treated, such as bleeding tissue. Plasma is discharged from a distal end. The high temperature of the discharged plasma allows for treatment of the affected tissue.
Owing to the recent developments in surgical technology, laparoscopic (keyhole) surgery is being used more often. Performing laparoscopic surgery requires devices with small dimensions to allow access to the surgical site without extensive incisions. Small instruments are also advantageous in any surgical operation for achieving good accuracy.
WO 2004/030551 (Suslov) discloses a prior-art plasma surgical device, which is intended for, among others, reducing bleeding in living tissue with plasma. This device comprises an anode, a cathode, and a gas supply channel for supplying plasma-generating gas to the device. Further, this plasma-generating device comprises at least one electrode arranged upstream of the anode. A housing connected to the anode, made of an electrically conductive material, encloses elements of the plasma-generating system and forms the gas supply channel.
It is desirable to provide a plasma-generating device capable of not only coagulation of bleeding living tissue, but also of cutting it.
With the device according to WO 2004/030551, generally a relatively high plasma-generating gas flow rate is required to generate a plasma flow capable of cutting. To generate a plasma flow with a suitable temperature at such flow rates, it is necessary to apply a relatively high operating electric current to the device.
It is desirable, however, to operate plasma-generating devices at relatively low operating electric currents, since high operating electric currents are often difficult to provide in certain environments, for example, in a medical environment. Also, as a general rule, a high operating electric current also requires extensive wiring, which can get unwieldy to handle during high precision procedures, for example, in laparoscopic surgery.
Alternatively, the device according to WO 2004/030551 could be formed with a relatively long plasma channel to generate a plasma flow with a suitable temperature at the required gas flow speeds. However, a longer plasma channel would make the device long and unwieldy for certain applications, for example, for medical applications, and especially for laparoscopic surgery.
For many applications, the generated plasma should be pure, i.e., have a low amount of impurities. It is also desirable that the discharged plasma flow has a pressure and a flow rate that are not harmful to a patient.
According to the above, there is a need for improved plasma-generating devices capable of effectively cutting biological tissue. The devices should be capable of being easily held and maneuvered. There is also a need for improved plasma-generating devices that can generate a pure plasma at lower operating currents and at lower gas flow rates.